<?php 
/*
View Library
Acts as an object wrapper for HTML pages with embedded PHP, called "views". 
Variables can be assigned with the view object and referenced locally within the view.
*/

class View {

	// Array of global variables
	protected static $_global_data = array();
	
	// View filename
	protected $_file;

	// Array of local variables
	protected $_data = array();	

	// Returns a new View object. If you do not define the "file" parameter, you must call [View::set_filename].
	// $view = View::instance($file);	
	public static function instance($file = NULL, array $data = NULL) {

		return new View($file, $data);
		
	}

	// Captures the output that is generated when a view is included.
	// The view data will be extracted to make local variables. 
	// This method is static to prevent object scope resolution.	
	// $output = View::capture($file, $data);
	protected static function capture($view_filename, array $view_data) {
		
		// Import the view variables to local namespace
		extract($view_data, EXTR_SKIP);

		if (View::$_global_data) {

			// Import the global view variables to local namespace
			extract(View::$_global_data, EXTR_SKIP);
		}

		// Capture the view output
		ob_start();

		try {
			// Load the view within the current scope
			include $view_filename;
			
		} catch (Exception $e){
			
			// Delete the output buffer
			ob_end_clean();

			// Re-throw the exception
			throw $e;
		}

		// Get the captured output and close the buffer
		return ob_get_clean();
	}

	// Sets a global variable, similar to [View::set], except that the
	// variable will be accessible to all views.	
	// View::set_global($name, $value);
	public static function set_global($key, $value = NULL) {
		
		if (is_array($key)) {
			
			foreach ($key as $key2 => $value) {
				
				View::$_global_data[$key2] = $value;
			}
			
		} else {

			View::$_global_data[$key] = $value;

		}
	}

	// Assigns a global variable by reference, similar to [View::bind], except
	// that the variable will be accessible to all views.
	// View::bind_global($key, $value);
	public static function bind_global($key, & $value) {
		
		View::$_global_data[$key] =& $value;

	}

	// Sets the initial view filename and local data. Views should almost
	// always only be created using [View::instance].
	// $view = new View($file);
	public function __construct($file = NULL, array $data = NULL) {

		if ($file !== NULL) {

			$this->set_filename($file);

		}

		if ($data !== NULL) {

			// Add the values to the current data
			$this->_data = $data + $this->_data;

		}
	}

	// Magic method, searches for the given variable and returns its value.
	// Local variables will be returned before global variables.
	// $value = $view->foo;
	// [!!] If the variable has not yet been set, an exception will be thrown.
	public function & __get($key) {

		if (array_key_exists($key, $this->_data)) {

			return $this->_data[$key];

		} elseif (array_key_exists($key, View::$_global_data)) {

			return View::$_global_data[$key];
			
		} else {
			
			throw new Exception("View variable is not set: $key");
			
		}
	}

	// Magic method, calls [View::set] with the same parameters.
	// $view->foo = 'something';
	public function __set($key, $value) {

		$this->set($key, $value);

	}

	// Magic method, determines if a variable is set.
	// isset($view->foo);
	// [!!] `NULL` variables are not considered to be set by [isset](http://php.net/isset).
	public function __isset($key) {

		return (isset($this->_data[$key]) OR isset(View::$_global_data[$key]));

	}

	// Magic method, unsets a given variable.
	// unset($view->foo);
	public function __unset($key) {

		unset($this->_data[$key], View::$_global_data[$key]);

	}

	/// Magic method, returns the output of [View::render].
	public function __toString() {
		
		try {
			
			return $this->render();
			
		} catch (Exception $e) {
			
			// Display the exception message
			return $e->getMessage();

		}
	}

	// Sets the view filename.
	// $view->set_filename($file);
	public function set_filename($file, $search_path = NULL) {
		
		//$search_path = SISTER_APP_PATH;
		
		if (($path = File::find('views/'.$file, $search_path)) === FALSE) {

			throw new Exception("The requested view $file could not be found");

		}

		// Store the file path locally
		$this->_file = $path;

		return $this;
	}

	// Assigns a variable by name. Assigned values will be available as a variable within the view file:
	// This value can be accessed as $foo within the view
	// $view->set('foo', 'my value');
	// You can also use an array to set several values at once:
	// Create the values $food and $beverage in the view
	// $view->set(array('food' => 'bread', 'beverage' => 'water'));
	public function set($key, $value = NULL) {

		if (is_array($key)) {

			foreach ($key as $name => $value) {

				$this->_data[$name] = $value;
			}
		} else {

			$this->_data[$key] = $value;

		}

		return $this;
	}

	// Assigns a value by reference. The benefit of binding is that values can
	// be altered without re-setting them. It is also possible to bind variables
	// before they have values. Assigned values will be available as a variable within the view file:

	// This reference can be accessed as $ref within the view
	// $view->bind('ref', $bar);
	public function bind($key, & $value) {

		$this->_data[$key] =& $value;

		return $this;
	}

	// Renders the view object to a string. Global and local data are merged and extracted to create local variables within the view file.
	// $output = $view->render();
	// Global variables with the same key name as local variables will be overwritten by the local variable.
	public function render($file = NULL) {

		if ($file !== NULL) {

			$this->set_filename($file);

		}

		if (empty($this->_file)) {
			
			throw new Exception('You must set the file to use within your view before rendering');
			
		}

		// Combine local and global data and capture the output
		return View::capture($this->_file, $this->_data);
	}

}
